The present invention relates to an apparatus, which irradiates a light-beam onto a sheet-film.
There has been well-known such a system that records an image onto a sheet-film, comprising a photosensitive material, such as a heat-processable photosensitive material, etc., by scanning a laser beam on the sheet-film under a drive controlling operation based on image data, radiographed by a medical image radiographing apparatus such as the X-ray CT or the MRI, etc., and transmitted to an image-recording apparatus, such as the Laser-Imager, etc.
Further, there has been developed and introduced into medical facilities such an image-recording apparatus that comprises both an image recording section to irradiate a laser beam onto the sheet-film and a processing section to develop the sheet-film.
In the abovementioned image-recording apparatus, a quality of the recorded image considerably depends on a scanning accuracy of a main-scanning unit for scanning the laser beam and a conveyance accuracy of a sub-scanning unit for conveying the sheet-film. Specifically, among the optical-parts comprising the main-scanning unit, a polygon mirror rotating at a high-velocity is sensitive to external vibrations, and is liable to induce unevenness of its rotating velocity. As a result, such the unevenness of rotating velocity of the polygon mirror causes unevenness of the recorded image.
For the purpose of solving the troubles stated above, there is proposed TOKKAISHO No. 61-230465 that discloses an image-recording apparatus having a construction in which an optical system (main-scanning unit) and a conveyance system (sub-scanning unit) are supported by the same supporting plate.
However, when there is employed the construction to support the optical system and the conveyance system with the same supporting plate, mass of the overall unit is increased, a height of the center of gravity of the overall unit is increased, and a position of the center of gravity of the overall unit on which the units are mounted is much higher than a height of a supporting position at which a supporting member supports the overall unit, and thereby, external vibrations cause the unit to make a pendulum-like turn, resulting in a concern of occurrence of the problems such as writing unevenness, etc.
For the problems mentioned above, there is proposed a construction to solve the problems by combining a plurality of vibration isolating members and regulating members in TOKKAIHEI No. 2-271136. However, this construction has not enough to be a satisfactory measure for the problems that external vibrations cause a main/sub-scanning unit to make a pendulum-like turn because a height of the center of gravity of the unit is increased and much higher than a height of supporting position at which a supporting member supports the unit, and has another problem that a space for providing plural supporting members is needed and low frequency vibrations are caused by a large-sized unit.
To suppress low frequency vibrations, there have been made attempts for lightening by dividing a sub-scanning unit and for lightening by thinning a wall thickness of a part and by changing to the resin materials, which are suggested in TOKKAISHO No. 58-17767. However, use of parts lightened excessively sometimes leads to a cost increase, and dispersion of accuracy created by a difference in thermal expansion caused by use of combined different materials is a problem, which cannot be ignored for forming minute images.
In the past, the vibration isolating member has been provided under the optical unit of a writing system, which has caused a height of the center of gravity of the optical unit to be much higher than a height of the vibration isolating member in many cases, and thereby, the optical unit has been caused by vibrations to tend to reciprocate linearly in the vertical, from-side-to-side and diagonal directions, and to make a pendulum-like turn. This pendulum-like turn has a tendency to be generated generally under the low frequency, and its decay time is longer than that of the vibration caused by the linear reciprocating motion.
In particular, in the case of the construction to have a film conveyance mechanism on the lower side of the optical unit, and in the case of the construction to have a film conveyance mechanism on the upper side of the optical unit, the height of the center of gravity of the optical unit grows greater, and the pendulum-like turn grows greater accordingly. To achieve stability of the unit under such construction, it is necessary to broaden intervals for attaching vibration isolating members, which leads to the large-sized apparatus.
Further, the scanning section that is made of various materials and employs a laser beam has resulted in unstable mass balance in many cases, because of the restriction in arrangement of functional parts derived from insurance of an optical path and of unbalance in materials and specific gravity.
Though there is proposed, in TOKKAISHO No. 61-230465, the construction to achieve stability of a unit by arranging respectively an optical unit and a film conveyance mechanism on both upper and lower sides of the same supporting plate, by supporting the supporting plate with a leg member to have an angle, and by supporting the lower portion of the leg member with the vibration isolating member, it is impossible to avoid the pendulum-like turn caused by vibrations because a position of the center of gravity of the optical unit is high and is away from the vibration isolating member located at the lower portion for mounting on the main body. Further, it is difficult, because of the structure of the leg member, to make the optical unit and the film conveyance mechanism to be capable of being mounted and dismounted, thus, maintenance work is still difficult, and it is impossible to avoid that the unit is made to be large in size and its mass increases.
Further, when mass of the unit grows greater, low frequency vibrations of the unit are increased, and it is necessary to use an elastic member such as rubber with low hardness to suppress the low frequency vibrations. Nevertheless, there is generated a shake of the unit caused by the vibrations, which has resulted in a fear of the problem that the unit comes in contact with surrounding members of the conveyance system. Even in the case of transportation of the unit, there have been problems including damages of precision optical parts caused by the excessive shake of the unit and damages caused by the contact between the unit and surrounding members of the conveyance system.